The present invention relates to a lens-fitted photographic film package having an exposure system, and more particularly to a lens-fitted photographic film package having a Z-shaped and elongated optical path.
In order to make it possible for anyone who does not carry a conventional camera to enjoy photographing with ease, various lens-fitted photographic film packages, which are disposable single-use cameras employing a conventional 35 mm film, are now on the market. Such a lens-fitted photographic film package (hereinafter referred to as a film package) has a light-tight casing which is factory-loaded with a 35 mm film. Because the taking lens of the film package is a fixed-focus lens, the user can take pictures only by depressing a shutter release button while aiming at a subject through a viewfinder formed in the film package. After the exposure of a frame, a film advancing wheel is rotated to wind the exposed frame into a cartridge. When substantially the entire length of the film strip is exposed and wound into the cartridge, the film package containing the exposed film is forwarded to a photofinisher without the need to perform a cumbersome rewinding operation. The photofinisher disassembles the light-tight casing or removes a cover member for a cartridge chamber to take out the cartridge containing the exposed film, which is then processed to make prints in a conventional manner. The obtained prints and the negative film are returned to the customer, and the casing is discarded. As the film package should resemble as much as possible a conventional photographic film, the film package has to be manufactured at low cost and should be small and light in weight for easy carrying.
Conventional film packages have a taking lens of about 35 mm focal length, and therefore function as a wide angle photographic camera when loaded with a 35 mm film. Accordingly, the size of the image of the main subjects recorded on the film may be smaller than desired by the customer, which may give disappointing results. In order to solve this problem, it would be desirable to use a long focal length taking lens, as in telephotography. But such a long focal length taking lens needs an elongated light path between the taking lens and the exposure station in which the film surface to be exposed is disposed. Such an elongated light path would result in increasing the thickness, namely the length in the axial direction, of the film package. Increasing the volume is incompatible with the above requirement for compactness.
It is well known in the art that light reflected from the inner wall surfaces of an exposure chamber, through which exposure light passes to the film surface, will cause flaring of the photographic image. In order to prevent this internal reflection, the inner wall surfaces of the exposure chamber of conventional film packages are roughened by molding and coated with a flat black paint to absorb light. But such a coating alone does not sufficiently prevent internal reflection in case of a long focal length taking lens, because a long focal length taking lens has a smaller angle of view and hence the light path will lie nearer the inner wall surfaces of the exposure chamber, thereby increasing the stray light that reaches the inner wall surfaces. In conventional reusable cameras such as compact cameras which can be repeatedly loaded with a new film, a velvety layer for absorbing light is provided on the inner wall surface of the exposure chamber by electrostatic fiber implanting. But such electrostatic fiber implanting is too costly for use in film packages which must be cheap.
It is also known in the art to provide on the inner wall surface of the exposure chamber light-cutting lines formed by a plurality of sharp and narrow grooves extending perpendicular to the optical axis. But such light-cutting lines do not sufficiently prevent internal reflection and moreover require an expensive metal mold for their formation.